Re: [time-nuts] KS-24361 Power Module Repair
OK, that explains your comment. This is most likely a silicone based potting compound. It's a bit softer than an eraser when cold. Very little of it was actually stuck to the board or components. If it had been a hard, epoxy-based covering, I wouldn't have bothered with it. Bob From: Chuck Harris cfhar...@erols.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, April 13, 2015 2:18 PM Subject: Re: [time-nuts] KS-24361 Power Module Repair No, I meant exactly what I said. When you are removing epoxy potting compound, put it in an oven set to 140C, and let it cook until up to temperature. The potting epoxy will become about as soft as pencil eraser rubber. You can then pick at it, and get pretty big chunks to come off. When the epoxy starts to feel hard again, pop it back in the oven. -Chuck Harris OBTW, we are not talking about crystal ovens here, but rather unpotting power supply modules. Al Wolfe wrote: This seems a bit toasty and is equivalent to 284F. Maybe meant 140F not C? An oven set to 140C is your friend when doing jobs like this. FWIW, the GE Progress Line two-way radios oscillator crystal holders had an octal base, held two crystals, and the heating element could be used on 6 volts or 12 volts depending on which way the holder was plugged in. I have no idea of how well they held the temperature. Always planned to use one with an external proportional controller but never got around to it. Al, k9si ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
I thought the context did a pretty good job of explaining it, but if it did not, I am sorry. Epoxy potting compound is a lot easier to remove than the silicone RTV based varieties... Although the silicone variety starts out soft, it is not crumbly. The epoxy sort loses its cohesiveness with its hardness when hot. If you stick a screwdriver into it, and twist, it pops off decent sized crumbs. What I typically do is take a dental probe that is dull, and slide it between the board and the potting compound, and strip off chunks of the potting material. Or I use small 1/8 inch blade screwdriver and do the same. It goes pretty fast... you avoid toroids, and things with fine wires, of course. The easiest way to remove silicone potting compounds is to take advantage of silicone rubber's voracious appetite for slurping up petroleum solvents. Put the item you want to strip in a container filled with naptha (aka lighter fluid, or fuel) and let it soak over night. By morning, there will be this highly bloated and fractured gelatinous mess all over the board. -Chuck Harris Bob Stewart wrote: OK, that explains your comment. This is most likely a silicone based potting compound. It's a bit softer than an eraser when cold. Very little of it was actually stuck to the board or components. If it had been a hard, epoxy-based covering, I wouldn't have bothered with it. Bob ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
Chuck, Very sorry, assumed you meant for operation. This makes perfect sense for deconstruction purposes. My bad. Al. k9si Date: Mon, 13 Apr 2015 15:18:14 -0400 From: Chuck Harris cfhar...@erols.com No, I meant exactly what I said. When you are removing epoxy potting compound, put it in an oven set to 140C, and let it cook until up to temperature. The potting epoxy will become about as soft as pencil eraser rubber. You can then pick at it, and get pretty big chunks to come off. When the epoxy starts to feel hard again, pop it back in the oven. -Chuck Harris OBTW, we are not talking about crystal ovens here, but rather unpotting power supply modules. Al Wolfe wrote: This seems a bit toasty and is equivalent to 284F. Maybe meant 140F not C? An oven set to 140C is your friend when doing jobs like this. snip ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
No, I meant exactly what I said. When you are removing epoxy potting compound, put it in an oven set to 140C, and let it cook until up to temperature. The potting epoxy will become about as soft as pencil eraser rubber. You can then pick at it, and get pretty big chunks to come off. When the epoxy starts to feel hard again, pop it back in the oven. -Chuck Harris OBTW, we are not talking about crystal ovens here, but rather unpotting power supply modules. Al Wolfe wrote: This seems a bit toasty and is equivalent to 284F. Maybe meant 140F not C? An oven set to 140C is your friend when doing jobs like this. FWIW, the GE Progress Line two-way radios oscillator crystal holders had an octal base, held two crystals, and the heating element could be used on 6 volts or 12 volts depending on which way the holder was plugged in. I have no idea of how well they held the temperature. Always planned to use one with an external proportional controller but never got around to it. Al, k9si ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
This seems a bit toasty and is equivalent to 284F. Maybe meant 140F not C? An oven set to 140C is your friend when doing jobs like this. FWIW, the GE Progress Line two-way radios oscillator crystal holders had an octal base, held two crystals, and the heating element could be used on 6 volts or 12 volts depending on which way the holder was plugged in. I have no idea of how well they held the temperature. Always planned to use one with an external proportional controller but never got around to it. Al, k9si ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
Yes, and for those hams amongst us TN's, these switchers produce copious amounts of RFI all over the HF bands. I replaced my DC/DC converters with external linears, to stop the pollution. -Doug W6DSR This particular module had +/- 15V, and +5V on board. I have never seen so many individual switching power supplies stuffed into a single module... They were all little 5 terminal IC's, with each running at whatever frequency it felt like... -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Harris Sent: Friday, April 10, 2015 9:52 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] KS-24361 Power Module Repair That is almost a carbon copy description of how I fixed a similar module in my Ball/Efratom MGPS unit on my GPSRb unit. An oven set to 140C is your friend when doing jobs like this. The guys that make these modules are trying to make them as small as possible, so they always use tantalum capacitors, and run them very close to their ratings... in this case, it was 18V on a 20V cap. This particular module had +/- 15V, and +5V on board. I have never seen so many individual switching power supplies stuffed into a single module... They were all little 5 terminal IC's, with each running at whatever frequency it felt like... -Chuck Harris Bob Stewart wrote: This is just a brief report, not a how-to. I got a KS_24361 with a bad Lucent power module. Having nothing to lose I thought I'd see if it came apart. After unsoldering it from the motherboard, I found the usual potting compound. Fortunately, the compound was only loosely attached to the board in the brick and was easy to pick off. After that, I used a pair of needle-nose pliers to work the board out of the casing. In spite of the pic below, I first gently pried up on the corners, in succession, until the corners released. Then I worked my way toward the middle, until the board came out. Be aware that there are two small inductors on the top side of the board that have metal covers that will probably stay in the potting compound. Just leave them there. When you push it all back together the covers will go back on the inductors. http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot while I had it on, so I figured there was a shorted component. As it turned out, it was a 15uF tantalum cap with a big brown spot on it. http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board at the upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg So, ordered the cap, put it on the board, then just pushed the pins into the motherboard for testing. I didn't even bother soldering it. http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the board back into the casing, and soldered it all back on the motherboard. I didn't bother repotting the bottom surface of the board. I attached the repaired KS to my good REF-0, and it's now working. Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
Hi I’ve seen the same failure on Efratom LPRO Rb’s on the input bypass cap. It’s a pretty common failure in general. Tantalum’s don’t really like very high surge currents / rapid voltage ramps. In normal bypass applications, restricting current surge / voltage ramps may be a bit tough on the power input side of a system. Bob On Apr 11, 2015, at 12:52 AM, Chuck Harris cfhar...@erols.com wrote: That is almost a carbon copy description of how I fixed a similar module in my Ball/Efratom MGPS unit on my GPSRb unit. An oven set to 140C is your friend when doing jobs like this. The guys that make these modules are trying to make them as small as possible, so they always use tantalum capacitors, and run them very close to their ratings... in this case, it was 18V on a 20V cap. This particular module had +/- 15V, and +5V on board. I have never seen so many individual switching power supplies stuffed into a single module... They were all little 5 terminal IC's, with each running at whatever frequency it felt like... -Chuck Harris Bob Stewart wrote: This is just a brief report, not a how-to. I got a KS_24361 with a bad Lucent power module. Having nothing to lose I thought I'd see if it came apart. After unsoldering it from the motherboard, I found the usual potting compound. Fortunately, the compound was only loosely attached to the board in the brick and was easy to pick off. After that, I used a pair of needle-nose pliers to work the board out of the casing. In spite of the pic below, I first gently pried up on the corners, in succession, until the corners released. Then I worked my way toward the middle, until the board came out. Be aware that there are two small inductors on the top side of the board that have metal covers that will probably stay in the potting compound. Just leave them there. When you push it all back together the covers will go back on the inductors. http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot while I had it on, so I figured there was a shorted component. As it turned out, it was a 15uF tantalum cap with a big brown spot on it. http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board at the upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg So, ordered the cap, put it on the board, then just pushed the pins into the motherboard for testing. I didn't even bother soldering it. http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the board back into the casing, and soldered it all back on the motherboard. I didn't bother repotting the bottom surface of the board. I attached the repaired KS to my good REF-0, and it's now working. Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
On 4/10/2015 4:27 PM, Bob Stewart wrote: This is just a brief report, not a how-to. I got a KS_24361 with a bad Lucent power module. Thanks a lot for that report Bob, I had no idea that it was possible to un-encapsulate those and get at the insides. I have one here that came to me dead, and I knew it had a shorted tantalum on the -15V output since I could see that from resistance checks. Chuck's tip about using an oven came too late for me, but after quite a struggle I opened mine up last night and found the culprit cap. No visible damage to it since the short must have shut the supply down. It now does power up and time will tell if I eventually get a green light :^) Dan - ac6ao ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
Bob Thanks for the pictures and clues. I have a bad lucent on a hp3801. It was just 1 of the supplies so I adapted an alternate switcher and it works just fine. That said there is hope I can go back in and fix it and also if need be the ones on the KS units I have. I have sensed there is a flake-y unit on one of them. Regards Paul WB8TSL On Sat, Apr 11, 2015 at 12:52 AM, Chuck Harris cfhar...@erols.com wrote: That is almost a carbon copy description of how I fixed a similar module in my Ball/Efratom MGPS unit on my GPSRb unit. An oven set to 140C is your friend when doing jobs like this. The guys that make these modules are trying to make them as small as possible, so they always use tantalum capacitors, and run them very close to their ratings... in this case, it was 18V on a 20V cap. This particular module had +/- 15V, and +5V on board. I have never seen so many individual switching power supplies stuffed into a single module... They were all little 5 terminal IC's, with each running at whatever frequency it felt like... -Chuck Harris Bob Stewart wrote: This is just a brief report, not a how-to. I got a KS_24361 with a bad Lucent power module. Having nothing to lose I thought I'd see if it came apart. After unsoldering it from the motherboard, I found the usual potting compound. Fortunately, the compound was only loosely attached to the board in the brick and was easy to pick off. After that, I used a pair of needle-nose pliers to work the board out of the casing. In spite of the pic below, I first gently pried up on the corners, in succession, until the corners released. Then I worked my way toward the middle, until the board came out. Be aware that there are two small inductors on the top side of the board that have metal covers that will probably stay in the potting compound. Just leave them there. When you push it all back together the covers will go back on the inductors. http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot while I had it on, so I figured there was a shorted component. As it turned out, it was a 15uF tantalum cap with a big brown spot on it. http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board at the upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg So, ordered the cap, put it on the board, then just pushed the pins into the motherboard for testing. I didn't even bother soldering it. http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the board back into the casing, and soldered it all back on the motherboard. I didn't bother repotting the bottom surface of the board. I attached the repaired KS to my good REF-0, and it's now working. Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 Power Module Repair
That is almost a carbon copy description of how I fixed a similar module in my Ball/Efratom MGPS unit on my GPSRb unit. An oven set to 140C is your friend when doing jobs like this. The guys that make these modules are trying to make them as small as possible, so they always use tantalum capacitors, and run them very close to their ratings... in this case, it was 18V on a 20V cap. This particular module had +/- 15V, and +5V on board. I have never seen so many individual switching power supplies stuffed into a single module... They were all little 5 terminal IC's, with each running at whatever frequency it felt like... -Chuck Harris Bob Stewart wrote: This is just a brief report, not a how-to. I got a KS_24361 with a bad Lucent power module. Having nothing to lose I thought I'd see if it came apart. After unsoldering it from the motherboard, I found the usual potting compound. Fortunately, the compound was only loosely attached to the board in the brick and was easy to pick off. After that, I used a pair of needle-nose pliers to work the board out of the casing. In spite of the pic below, I first gently pried up on the corners, in succession, until the corners released. Then I worked my way toward the middle, until the board came out. Be aware that there are two small inductors on the top side of the board that have metal covers that will probably stay in the potting compound. Just leave them there. When you push it all back together the covers will go back on the inductors. http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot while I had it on, so I figured there was a shorted component. As it turned out, it was a 15uF tantalum cap with a big brown spot on it. http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board at the upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg So, ordered the cap, put it on the board, then just pushed the pins into the motherboard for testing. I didn't even bother soldering it. http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the board back into the casing, and soldered it all back on the motherboard. I didn't bother repotting the bottom surface of the board. I attached the repaired KS to my good REF-0, and it's now working. Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
